During the Muncher chase, Ecto-1's blue lights are off. The internal shot of the restaurant shows Ecto-1 passing the window with the lights flashing. In the exterior shots, the lights are off again.
When Callie meets Gary in the desert, and changes her clothes to a gold dress, she is barefoot. When climbing the steps to take her place beside Gozer, she is wearing high heels. When she hits the foot-pedal to trap Gozer, she is again barefoot.
After opening the ghost trap, the windshield on Grooberson's car is broken. Later, when they arrive home after the jail scene, his windshield is intact. Later, during the terror dog chase, his windshield is broken again.
In the test firing scene closeup with Phoebe, the red tubing on the end of the neutrona wand has fallen out of the brass banjo. It's fixed in the next scene.
When the kids steal back Ecto 1 from the police station, they speed off with the lights blaring and sirens wailing. In the next shot, they are both off. In the following shot, when crossing the bridge, both the lights and sirens are on again.
The marshmallow men light up and use a demonstration grill at Walmart. A demonstration grill could not be lit, even by accident, because it requires propane gas to light, and storing propane inside a commercial building is illegal.
Phoebe could, in theory, generate 220V from a pair of 110V lines, but she would have had to make alterations at the circuit breaker. Since she was using a 110V from a neighbor, she'd have to alter their circuit breaker as well.
When Trevor is about to try and start the Ecto-1, the distributor cap is seen on top the motor and not properly installed. In this position the motor could not have started nor would the hood be able to close.
Podcast describes the Krakatoa volcanic eruption of 1883 as the most powerful in human history. Mount Tambora's eruption in 1815 was significantly more powerful. Tambora is the only modern volcanic eruption with a Volcanic Explosivity Index of 7. Krakatoa was one of several in a 100-year span with a VEI of 6. Tambora's eruption was so catastrophic that 1816 came to be known as "the Year Without a Summer", and the resulting famines killed thousands. Krakatoa is better known because it occurred after the invention of the telegraph. Podcast described Krakatoa as the "most violent earthquake in history," a more subjective term than "most powerful."
The film contains several written references to the Biblical book of "Relevations." The book is called "Revelation," with no "S" at the end. It's a nod to the original Ghostbusters (1984), when Ray Stantz made the same mistake.
Egon is know as a "dirt farmer". The store clerk mentions that Egon never planted anything or took care of the fields. In the first scene when Egon is racing back to his farm, the truck is run off the road into a corn field. Egon runs back from the wrecked truck through a tall corn field. Gozer arrives at Egon's farm and walks into the trap area from a corn field. When Trevor goes on a joyride after repairing Ecto-1, he drives through a wheat field. Planting the traps in the bare earth is the "dirt farming". The surrounding fields are neighboring farms.
Phoebe finds the trap Egon hid under the living room floor, containing one of the terror dogs. When she pulls it out of the floor, no trap pedal is present. The next time the trap is shown, at the school, it's plugged into a pedal. The pedal and connecting wire are both visible when Egon holds out the ghost trap to lure Zuul towards him, it's possible he put the pedal in after the trap and it just wasn't shown.
When Podcast takes the Polaroid photo, he shakes it vigorously. Back when Polaroids were popular, impatient consumers would shake the photos, hoping to speed up the chemical reaction. Polaroid publicly warned consumers that shaking the photo as it developed could damage it. Everyone shakes Polaroid photos, it wouldn't be absurd to see someone, especially a 12 year old, also shake one.
Trevor drives the Ecto-1 at speed through a wheat field. Instead of bouncing, the car behaves as though it's being driven on a smooth surface with good traction. The car also doesn't appear to damage the wheat.
When Grooberson, Phoebe, and Podcast are attempting to open the ghost trap, they use additional power supplied by the school bus batteries. However, on most school buses, the batteries are in a compartment on the left side of the bus, under the stop sign, behind a latched door. The jumper cables in this scene are most likely attached to a coolant line that runs to and assists in cooling the automatic transmission.
At the police station, Callie pulls the neutrona wand out of Phoebe's hand and the clear barrel lights up with white LEDs. They're used to indicate when the editors should add the proton stream effect.
Callie buys Behr paint at the small-town hardware store. Behr is only available at Home Depot.
When the family first arrive at the 'dirt farm' and the house begins to shake a tall tower of books can be seen in the background and despite the house shaking quite violently the tower of books remain in place. Not only that, but they don't move or fall individually and appear to have been attached together and more than likely secured to the floor to prevent such an incident from occurring.
Paul Rudd's character is called Mr. Grooberson, and this is how he introduces himself to his summer school class in the first scene. However, his name on the board behind him says 'Mr. Goooberson.'
When Phoebe is holding a flashlight to the years along the wall in Gozer's underground temple, the year 2019 is briefly visible on the wall. In the next shot where the focus is brought to the year indicating the present, the year is seen 2021.
In the final act, Trevor enters the back of the Ecto-1 with Podcast. A door slams shut, yet no doors are shown opening or closing.
Grooberson wears a key ring on his belt, yet the keys never make a sound even when he's running.
When Trevor stands on the right of the screen and pulls the tarp off the Ecto-1, the camera operator's shadow is visible at the lower left corner of the screen.
When Grooberson, Phoebe, and Podcast are trying to open the trap, a person wearing a shirt similar to Grooberson's is visible in the open bus doorway behind Phoebe. It's not a reflection, as the figure does not move when he moves, and it's gone after a few shots.
Mr. Lube, a uniquely Canadian franchise, is visible in the background during the Walmart scene.
The yellow-on-red display signs in Walmart are only used in Canadian stores.
The Walmart VisionCentre uses the Canadian spelling.
When the Ecto-1 is on the dirt road chasing after Muncher, Podcast claims he is "in range" to capture Muncher. Podcast isn't wearing the Ecto-goggles, nor is he in the front of the car, so he couldn't possibly know that.
One character yells during the showdown that they're using "billions of electron volts" to bust Gozer. An electron volt is the energy of an electron. Billions of eV are still less than the kinetic energy of a fly.
Gary tells Callie that before fracking, Oklahoma "never had earthquakes for centuries." Oklahoma has had several earthquakes over the past 200 years. On April 9, 1952, a magnitude 5.5 earthquake occurred near El Reno, in Canadian County. It caused a 50 foot-long crack in the Capitol building in Oklahoma City, and was felt throughout Oklahoma and in parts of seven other states.
When Grooberson is talking to Phoebe for the first time in the school, the word "spherical" behind him on the white board is misspelled "shperical".
Grooberson says he set up geophones to locate the seismic anomaly, but he can't triangulate. Phoebe replies, "Are you using three?", and Grooberson responds, "Yeah, I know how many sides a triangle has." Triangulation uses two bearings, directional readings from sensors, from known locations to identify a third point. With two geophones, the third point of the triangle would be the source of the disturbance.
Capturing Muncher doesn't follow the routine. The proton-pack energy stream 'captures' the ghost. Once Mucher was captured, Trevor could hit the brakes and stop Ecto-1. There was no reason for him to keep racing after the ghost to keep up with it, and the the ghost wasn't pulling the car through town. However, these were young kids who don't know fully how the equipment works and may not have realised in the heat of the moment that the car could just be stopped at this point.